It seems that much of the page referenced above is really part of the APIs and
deserves to be included in their documentation, rather than a page floating on
the website. Of course some of what is there is not official specifications of
how the IDE must behave, but I think the content can be separated into:
1. how NbBundle and localization and branding work technically
2. unsupported but currently true aspects of how to package localized/branded
resources (locale/ JARs etc.)
3. other conventions specific to the NetBeans project, e.g. #NOI18N marker in
bundles, not controlled by the APIs
4. tips and techniques, e.g. bundle debugging mode, or the how-to on localizing
manifests
Probably 1. should be in APIs marked as official, 2. as unofficial, 3. left
where it is (but linked to from the APIs for convenience), 4. perhaps put in
APIs as unofficial info or perhaps left where it is but linked to.
At a minimum, the existing page should be linked to from the list of "Other
Documents" in the APIs summary page, so people know it exists.

Also document mistakes such as these:
ResourceBundle bundle = ResourceBundle.getBundle(...);
bundle.getString("KEY");
// should have used NbBundle which permits branding
Icon i = new ImageIcon(Class.getResource("ide.gif"));
// should have used nbresloc:/.../ide.gif
// or NbBundle.findLocalizedResource
<folder name="Templates">
<file name="Something.java" url="Something.java.tmpl">
<attr name="template" boolvalue="true"/>
<!-- using an unlocalized name here -->
<!-- should have used SystemFileSystem.localizingBundle -->
</file>
</folder>